The present invention relates to a transformerless system for simultaneously transmitting logic information signals independently and bidirectionally between first and second information stations using only a single pair of transmission wires, while maintaining electrical isolation between said information stations. The system can be advantageously used for example to interconnect two computers, a computer and a keyboard and the like.
Although systems for bidirectional transmission of information on a single pair of wires are known to the art, each of these known systems has certain drawbacks. For example, some known systems require carrier modulation with transformer coupling to achieve common-mode isolation. Other known systems require a floating power supply or are incapable of simultaneous asynchronous transmission.
It is not believed that the known art provides a system in which a logic signal is transmitted through a photocoupler from a first to a second information station in the form of a voltage signal on a transmission line, while simultaneously another logic signal is transmitted through a photocoupler in the reverse direction in the form of a current signal on said transmission line. It is the object of the present invention to provide such a simultaneous, bidirectional transmission system.